The invention relates to a drawbar arrangement by which a drawn implement is coupled to a vehicle such as an agricultural tractor or utility vehicle, and more particularly, to a drawbar which has an adjustable length. It is well known to pivotally mount a drawbar at the rear of a tractor so that implements, such as a trailer or a mower can be coupled to the tractor. For example, a pivoted drawbar is shown in DE-PS-492 300. This pivoted drawbar is provided with spaced apart bores which can be aligned selectively with bores in transverse straps that are attached to the vehicle chassis. The length to which this pivoted drawbar extends beyond the rear end of the vehicle can be selected by inserting a locking pin through the aligned bores.
This type of adjustable length drawbar cannot be used in many cases due to the extent of the longitudinal supports and transverse straps. For example, the rear region of an agricultural tractor is occupied generally by a multitude of towing, mounting and hitch structures which limit the available space. In the design shown in DE-PS-492 300 the longitudinal supports and transverse straps restrict or make impossible the operation of the towing and mounting arrangements.
In many agricultural tractors an adjustable length pivoted drawbar is provided in order to comply with the requirements of various coupled implements. This is necessary since the distance between the coupling point and the end of the power take-off shaft may be different for the different implements that can be coupled to the tractor. The differing operating lengths are standardized by ISO or SAE.
Due to the limited space available it is common practice to attach the pivoted drawbar to the vehicle from underneath, for example, to the differential housing. If the distance between the coupling point and the end of a power take-off shaft is changed, then the operator must adjust the drawbar from the underside of the tractor. This may be accomplished by releasing a locking pin and moving the pivoted drawbar into the desired position and then manually securing the desired operating length by inserting the locking pin into an appropriate hole in the pivoted drawbar. This work is uncomfortable and requires a relatively large amount of time. The coupling process, in which the operator backs the tractor to the implement to be coupled, is difficult if the coupling point of the pivoted drawbar is very close to the rear of the tractor and cannot be visually inspected from the operator's seat.